1. Field of the Invention
The present invention relates to a neighborhood type (The correspondence distance is approximately 1 m.) non-contact IC card reader/writer by which electric power and sending data are supplied to a non-contact IC card, and receiving data is acquired from the non-contact IC card by a change in the load. That is, the present invention relates to an integrated antenna type non-contact IC card reader/writer, the size of which is reduced when the antenna and the control board are integrated into one body.
2. Description of the Related Art
Conventionally, a reader/writer system using IC cards is generally referred to as an IC card system. For example, this reader/writer system is being put into practical use for the physical distribution system, traffic system and air freight management system in which the frequency band of 13.56 MHz is used. This system includes: an IC card on which an IC chip and antenna coil are provided on one piece of card made of resin; and a reader/writer conducting correspondence with this IC card. This reader/writer is provided with a loop antenna, which constantly or intermittently sends electric power and sending data and acquires receiving data from IC card located in a range capable of receiving electric power and sending data.
As an example, a conventional non-contact IC card system and loop antenna described in “Official gazette of JP-A-2002-279362” are shown in FIG. 5. In this connection, FIG. 5 is a conceptional view showing a conventional non-contact IC card reader/writer. As shown in FIG. 5, the antenna (loop antenna) 201 and reader/writer (R/W) 203 are connected with each other by the coaxial cable 202. Further, the reader/writer 203 is connected with the control unit 204. The non-contact IC card (IC tag) 207 is stuck on the load 206 conveyed on the conveyance line 205. Supplying of electric power and sending and receiving of data are conducted between this non-contact IC card 207 and the antenna 201 connected with the reader/writer 203, and assortment and management are conducted on the load 206. As shown in FIG. 5, the conventional antenna 201 and the reader/writer 203 are arranged at distant places and connected with each other by the long coaxial cable 202.
A positional relation among the antenna 201, the long coaxial cable 202 and the reader/writer 203 is briefly shown in FIG. 6. In this connection, FIG. 6 is a simplified view showing a conventional non-contact IC card reader/writer. In FIG. 6, the conventional neighborhood type non-contact IC card reader/writer includes: an antenna portion composed of the loop antenna 208 and the antenna radome 209 made of resin for accommodating the loop antenna 208; and a reader/writer 203 for supplying electric power and sending data to the antenna portion 201 and for acquiring receiving data. The antenna portion 201 and the reader/writer 203 are connected with each other by the coaxial cable 202.
A conventional neighborhood type non-contact IC card reader/writer described in “Official gazette of JP-A-2002-063552” is shown in FIG. 7. In this connection, FIG. 7 is a conceptional view showing a conventional non-contact IC card reader/writer. As shown in FIG. 7, the conventional neighborhood type non-contact IC card reader/writer is assembled in such a manner that the antenna portion 201 and the control board 210 are made to come close to each other being laminated on each other. Therefore, a size of the entire device in the thickness direction is increased and an entire region on one side of the antenna opening is substantially covered with the control board 210.
As described above, in the conventional neighborhood type non-contact IC card reader/writer shown in FIGS. 5 and 6, the antenna portion 201 and the reader/writer 203 are separate from each other and connected by the coaxial cable 202. Due to this constitution, the following problems may be encountered. In the case of installing this device, when the coaxial cable 202 is laid round the device, the neighboring antenna 201 is affected by the coaxial cable 202, and the resonance frequency is shifted (transition of the resonance frequency). Accordingly, it becomes necessary to adjust the resonance frequency by a trimmer condenser (not shown) provided in the antenna resonance circuit.
Further, the following problems may be encountered. In some cases, since a place in which the device is installed is restricted, length of the coaxial cable 202 is greatly increased. Accordingly, electric power to be transmitted is lowered and further data to be received is lost by an increase in the cable transmission loss. Furthermore, since length of the coaxial cable 202 is increased, the coaxial cable 202 tends to be affected by an obstruction wave and noise given from the outside.
Furthermore, the following problems may be encountered. The conventional neighborhood type non-contact IC card reader/writer shown in FIG. 7 is assembled in such a manner that the antenna portion 201 and the control board 210 are made to come close to each other being laminated on each other. Therefore, a size of the entire device in the thickness direction is increased and an entire region on one side of the antenna opening is substantially covered with the control board 210. Accordingly, an electromagnetic field generated by the antenna is interrupted. Therefore, even when an intensity of electric power of sending is increased, the electric power to be sent into the space is lost, which decreases a distance of correspondence.